There are a number of things that could trigger a photosensitive seizure. Because people’s sensitivities are so individual, not everything will affect every person with photosensitive epilepsy. The following are some of the things that people ask us about:
Bicycle lights (red and white)
UK law says that these lights mustn’t flash at less than one or more than 4 flashes a second. Provided the lights comply with the law, they are unlikely to cause a problem.
Some ceiling fans can rotate at a fast speed. Looking at light through them could be a seizure trigger.
Christmas lights that flash
There is no UK law that covers the flash frequency of Christmas lights. It’s therefore possible that they could trigger a seizure.
Computer screens are unlikely to be a seizure trigger. However if there are flashing or flickering images, or some types of pattern on the screen, these could be a seizure trigger.
Flashing novelty badges
These can flash at any rate. It is therefore possible that they could be a seizure trigger.
Unless what is shown on an interactive whiteboard flashes or flickers, or has some types of pattern, they are unlikely to be a seizure trigger.
Light bulbs (any type)
These are only a possible seizure trigger if they are faulty. Otherwise, they shouldn’t cause a problem.
These are some examples of patterns that could be seizure triggers:
- High contrast patterns such as black and white stripes
- Striped or patterned materials and walls
- Patterns in some television programmes, video or electronic games
- A moving escalator
We have been unable to find any current official guidance on the recommended flash rate of strobe lights. However, it is possible that they could be a seizure trigger.
The American Epilepsy Foundation’s professional advisory board recommends that:
- The flash rate be kept to under 2 hertz with breaks every so often between flashes
- Flashing lights should be placed at a distance from each other and set to flash together at the same time to avoid an increase in the number of individual flashes
The word hertz refers to something that happens in a second. For example, it can mean the number of times something flashes or flickers in 1 second.
These may trigger a seizure if the tubes flicker. Otherwise, they shouldn't cause a problem.
Looking directly at certain patterns caused by sunlight could be a seizure trigger for some people. Examples of these situations are:
- Sunlight through slatted blinds
- Sunlight through trees, viewed from a moving vehicle
- Sunlight reflected off moving water or off snow
- Sunlight through moving leaves
- Sunlight through railings, as you move past them
Modern TV screens don’t flicker so are unlikely to be a seizure trigger for most people. However, if a programme shows images that flash or flicker, these could be a seizure trigger for some people.
Large wind turbines rotate at a rate that is unlikely to trigger a seizure. Smaller turbines can rotate at a faster rate. When these smaller turbines create a shadow and/or flicker effect with the sun, they could be a seizure trigger.
If you are concerned about flashing artificial lights, you can complain to your local council. They should consider complaints about ‘nuisance lights’, but they may not take account of someone’s photosensitive epilepsy. This is because they only have to consider how the nuisance affects the ‘average person’, not people with ‘rare sensitivities.’
If you would like to see this information with references, visit the Advice and Information references section of our website or contact our Epilepsy Action freephone Helpline on 0808 800 5050.
This information has been produced under the terms of Epilepsy Action's information quality standards.
- Updated June 2018To be reviewed June 2021